The bladder, prostate and urethra
The bladder
- The bladder is pyramidal in shape
- When empty its is an extraperitoneal structure
- Its superior surface is covered by the pelvic peritoneum
- Anteriorly its lies behind the pubis bone
- Apex is attached to the umbilicus by the median umbilical ligament
- This represents the remnant of the foetal urachus
- The inferolateral surface is related to the levator ani and
obturator internus muscles
- The bladder neck fuses with the prostate in men
- In women the uterus lies against its posterosuperior surface
- The base is related to the vagina and cervix
- In men, the base is related to the rectum, vas deferens and seminal
vesicles
- The ureters join the bladder at the upper lateral angles
- On the interior surface of the bladder the ureteric orifices are
joined by the interureteric ridge
- With the urethral orifice this forms an area know as the trigone
- As the bladder distends it strips the peritoneum off the anterior
abdominal wall
- The wall is made if smooth muscle and is lined by transitional
epithelium
- The bladder has two sphincters
- Internal sphincter - smooth muscle at bladder neck
- External sphincter - voluntary muscles distal to the internal
sphincter
- The blood supply is from the superior and inferior vesical branches
of the internal iliac artery
- Lymphatic drainage is to the iliac and para-aortic nodes
- The bladder has both a motor and sensory nerve supply
- The motor supply is autonomic
- A sympathetic and arises from L1 / L2 and is inhibitory
- A parasympathetic supply arises from S2 - S4 and is motor to the
detrusor muscle
- The sensory supply is parasympathetic
The prostate
- The prostate is fibromuscular and glandular organ
- Surround the beginning of the urethra in men and has 5 lobes
- Anterior lobe
- Posterior lobe
- Middle lobe
- Lateral lobes x2
- Above its is continuous with the base of the bladder
- Below the apex sits on the sphincter urethrae in the deep perineal
pouch
- Posteriorly it is separated from the rectum by Denonvillier's fascia
- Anteriorly it is separated from the pubis by extraperitoneal fat
- Surrounded by prostatic venous plexus
- Ejaculatory ducts formed by the fusion of the vas deferens and
seminal vesicles
- Enter upper posterior part of the prostate and open into the urethra
- Blood supply is from the inferior vesical artery
The male urethra
- The male urethra is about 20 cm in length
- Divided into three parts
The prostatic urethra
- The prostatic urethra is about 4 cm in length
- Posterior wall has a longitudinal elevation know as the urethral
crest
- Along each side is the prostatic sinus
- In the middle of the crest is an elevation known as the verumontanum
- Prostatic utricle opens into the verumontanum
- On each side of the utricle opens the ejaculatory ducts
The membranous urethra
- The membranous urethra is about 2 cm in length
- Narrowest part of the urethra
- Traverses the external urethral sphincter in deep perineal pouch
The spongy urethra
- The spongy urethra is about 15 cm in length
- Traverses the corpus spongiosum of the penis
- External urethral orifice is the narrowest part
- Immediately within the meatus the urethra dilates into a terminal
fossa
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Author:
Dr Shakeeb Khan |
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